Angle encoder

Abstract

An angle encoder for determining the pitch (or yaw) angle of a gyroscopic mass with respect to the pitch (or yaw) axis of a missile in flight is shown to be the combination of: (a) an optical encoder pattern disposed on the periphery of the gyroscopic mass, such pattern preferably being divided into a substantially equal reflective portion and a nonreflective portion; (b) an optical sensor arrangement having a limited field of view, such arrangement being mounted on the body of the missile to provide a first signal whose level is indicative of the reflective or nonreflective portion in the limited field of view; and (c) circuitry for converting the first signal into a signal indicative of the pitch (or yaw) angle of the missile.

What is claimed is: 
     
       1. In a guided missile incorporating a guidance system wherein a gyroscopic mass with a periphery in the form of a zone of a sphere rotatable about a rotational axis and a gyroscopically stabilized platform are supported on at least one set of gimbals to permit angular movement between such platform and the body of such missile about a reference axis defined by at least one set of gimbals, such arrangement comprising: (a) an optical encoder pattern disposed on the periphery of the gyroscopic mass, such encoder pattern providing substantially equally-sized first and second portions separated by a spiral line, the reflectivity of the first and second portions differing; and   (b) optical sensing means including a sensor assembly affixed to the guided missile adjacent to the reference axis near the optical encoder pattern to produce, during each revolution of the gyroscopic mass, an output signal indicative of any angular movement between the gyroscopically stabilized platform and the body of the guided missile about the reference axis, the sensor assembly comprising: (i) a first optical transmission means including a first optical fiber having a first end disposed adjacent to the reference axis near the optical encoder pattern and a second end spaced from the first end within the body of the guided missile; and   (ii) a light emitting diode disposed near the second end of the first optical fiber whereby light from such diode is directed to a limited area on the periphery of the gyroscopic mass.     
     
     
       2. The arrangement as in claim 1 wherein the sensor assembly comprises, additionally: (a) a second optical transmission means including a second optical fiber having a first end adjacent to the first end of the first optical fiber to receive light reflected from the limited area on the periphery of the gyroscopic mass and direct such light to a second end of the second optical fiber within the body of the guided missile; and   (b) a photocell disposed adjacent to the second end of the second optical fiber to convert light from such fiber to a corresponding electrical signal.   
     
     
       3. The arrangement as in claim 2 comprising, additionally: (a) means, responsive to the corresponding electrical signal out of the photocell, for converting such signal to a gating signal having a first value during each revolution of the gyroscopic mass when the limited area on the periphery of the gyroscopic mass corresponds with the first portion of the optical encoder pattern and a second value when such area corresponds with the second portion of the optical encoder pattern; and   (b) counting means, responsive to clock pulses when the gating means has the first value, to produce a count indicative of the output signal.   
     
     
       4. In a guided missile incorporating a guidance system wherein a gyroscopic mass with a nominally reflective periphery in the form of a zone of a sphere rotatable about a rotational axis and a gyroscopically stabilized platform are supported on at least one set of gimbals to permit angular movement between such platform and the body of such missile about a reference axis defined by the at least one set of gimbals, such arrangement comprising: (a) an optical encoder pattern disposed on the nominally reflective periphery of the gyroscopic mass, such encoder pattern including: (i) a timing line corresponding to an arc of a great circle co-planar with the rotational axis and intersecting the periphery, such timing line being substantially nonreflective; and   (ii) a spiral line, such line being substantially nonreflective; and     (b) optical sensing means including a sensor assembly affixed to the guided missile adjacent to the reference axis near the optical encoder pattern to produce, during each revolution of the gyroscopic mass, an output signal indicative of any angular movement between the gyroscopically stabilized platform and the body of the guided missile about the reference axis.